diff --git a/src/libcore/container.rs b/src/libcore/container.rs
new file mode 100644
index 00000000000..619622ceb95
--- /dev/null
+++ b/src/libcore/container.rs
@@ -0,0 +1,24 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Container traits
+
+pub trait Set<T> {
+    /// Return true if the set contains a value
+    pure fn contains(&self, value: &T) -> bool;
+
+    /// Add a value to the set. Return true if the value was not already
+    /// present in the set.
+    fn insert(&mut self, value: T) -> bool;
+
+    /// Remove a value from the set. Return true if the value was
+    /// present in the set.
+    fn remove(&mut self, value: &T) -> bool;
+}
diff --git a/src/libcore/core.rc b/src/libcore/core.rc
index b800564b8e1..24623f20c80 100644
--- a/src/libcore/core.rc
+++ b/src/libcore/core.rc
@@ -122,6 +122,7 @@ pub mod to_bytes;
 pub mod clone;
 pub mod io;
 pub mod hash;
+pub mod container;
 
 
 /* Common data structures */
diff --git a/src/libcore/send_map.rs b/src/libcore/send_map.rs
index 4cd3502bd62..5c7b0643d3d 100644
--- a/src/libcore/send_map.rs
+++ b/src/libcore/send_map.rs
@@ -1,4 +1,4 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -46,6 +46,8 @@ pub trait SendMap<K:Eq Hash, V: Copy> {
 
 /// Open addressing with linear probing.
 pub mod linear {
+    use iter::BaseIter;
+    use container::Set;
     use cmp::Eq;
     use cmp;
     use hash::Hash;
@@ -442,7 +444,7 @@ pub mod linear {
         }
     }
 
-    impl<K:Hash IterBytes Eq, V: Eq> LinearMap<K, V>: cmp::Eq {
+    impl<K:Hash IterBytes Eq, V: Eq> LinearMap<K, V>: Eq {
         pure fn eq(&self, other: &LinearMap<K, V>) -> bool {
             if self.len() != other.len() { return false; }
 
@@ -460,6 +462,47 @@ pub mod linear {
             !self.eq(other)
         }
     }
+
+    pub struct LinearSet<T: Hash IterBytes Eq> {
+        priv map: LinearMap<T, ()>
+    }
+
+    impl <T: Hash IterBytes Eq> LinearSet<T>: BaseIter<T> {
+        /// Visit all values in order
+        pure fn each(&self, f: fn(&T) -> bool) { self.map.each_key(f) }
+        pure fn size_hint(&self) -> Option<uint> { Some(self.len()) }
+    }
+
+    impl <T: Hash IterBytes Eq> LinearSet<T>: Eq {
+        pure fn eq(&self, other: &LinearSet<T>) -> bool { self.map == other.map }
+        pure fn ne(&self, other: &LinearSet<T>) -> bool { self.map != other.map }
+    }
+
+    impl <T: Hash IterBytes Eq> LinearSet<T>: Set<T> {
+        /// Return true if the set contains a value
+        pure fn contains(&self, value: &T) -> bool {
+            self.map.contains_key(value)
+        }
+
+        /// Add a value to the set. Return true if the value was not already
+        /// present in the set.
+        fn insert(&mut self, value: T) -> bool { self.map.insert(value, ()) }
+
+        /// Remove a value from the set. Return true if the value was
+        /// present in the set.
+        fn remove(&mut self, value: &T) -> bool { self.map.remove(value) }
+    }
+
+    impl <T: Hash IterBytes Eq> LinearSet<T> {
+        /// Create an empty LinearSet
+        static fn new() -> LinearSet<T> { LinearSet{map: LinearMap()} }
+
+        /// Return the number of elements in the set
+        pure fn len(&self) -> uint { self.map.len() }
+
+        /// Return true if the set contains no elements
+        pure fn is_empty(&self) -> bool { self.map.is_empty() }
+    }
 }
 
 #[test]
diff --git a/src/libstd/treemap.rs b/src/libstd/treemap.rs
index b5f60a66978..1b20b35bda1 100644
--- a/src/libstd/treemap.rs
+++ b/src/libstd/treemap.rs
@@ -14,6 +14,7 @@
 
 #[forbid(deprecated_mode)];
 
+use core::container::Set;
 use core::cmp::{Eq, Ord};
 use core::option::{Option, Some, None};
 use core::prelude::*;
@@ -197,6 +198,21 @@ impl <T: Eq Ord> TreeSet<T>: Eq {
     pure fn ne(&self, other: &TreeSet<T>) -> bool { self.map != other.map }
 }
 
+impl <T: Ord> TreeSet<T>: Set<T> {
+    /// Return true if the set contains a value
+    pure fn contains(&self, value: &T) -> bool {
+        self.map.contains_key(value)
+    }
+
+    /// Add a value to the set. Return true if the value was not already
+    /// present in the set.
+    fn insert(&mut self, value: T) -> bool { self.map.insert(value, ()) }
+
+    /// Remove a value from the set. Return true if the value was
+    /// present in the set.
+    fn remove(&mut self, value: &T) -> bool { self.map.remove(value) }
+}
+
 impl <T: Ord> TreeSet<T> {
     /// Create an empty TreeSet
     static pure fn new() -> TreeSet<T> { TreeSet{map: TreeMap::new()} }
@@ -215,19 +231,6 @@ impl <T: Ord> TreeSet<T> {
         self.map.each_key_reverse(f)
     }
 
-    /// Return true if the set contains a value
-    pure fn contains(&self, value: &T) -> bool {
-        self.map.contains_key(value)
-    }
-
-    /// Add a value to the set. Return true if the value was not
-    /// already present in the set.
-    fn insert(&mut self, value: T) -> bool { self.map.insert(value, ()) }
-
-    /// Remove a value from the set. Return true if the value was
-    /// present in the set.
-    fn remove(&mut self, value: &T) -> bool { self.map.remove(value) }
-
     /// Get a lazy iterator over the values in the set.
     /// Requires that it be frozen (immutable).
     pure fn iter(&self) -> TreeSetIterator/&self<T> {